Coatings for ensuring run-in and emergency operation properties having a functional/gradual structure have been known for some time, and the composition of such coatings must strike a balance between friction-minimizing and wear-resistance properties. For this reason, highly wear-resistant components such as connecting rods in particular have carbon fibre-reinforced coatings, for example with a high roughness value, but this can be disadvantageous with respect to process monitoring. In addition, such hard carbon fibers have an abrasive effect on aluminium counterfaces, which can lead to undesirable polishing effects or the formation of grooves.
WO 2012/041769 A2 discloses a generic piston for an internal combustion engine having a shaft coating with a wear-resistant inner layer composed of a polymer matrix with ceramic particles dispersed therein, aramid fibers and/or carbon fibers and an outer layer composed of a polymer matrix with solid lubricants dispersed therein. The purpose is to provide a functional inner layer that is applied directly to the surface of the piston, as well as a wear-resistant outer layer (substrate layer) by means of which run-in behaviour and in particular scuff resistance are to be improved. The friction-minimizing coating is also intended to allow reduction of fuel consumption and CO2 emissions during operation of the internal combustion engine.
A further generic piston with a dual-layer shaft coating is known from EP 1 894 987 A1.
However, a drawback of the pistons known from the prior art is that production of the coatings is relatively energy-intensive.